I've heard a story about SV startup (onsite) employees stealing their startup's code base and launching their own company with it. It turned out to be more successful than the original one, which eventually tanked. The owners tried going to court, but they didn't have enough proof to get a search warrant (or whatever the proper legal term is here) for their fraudulent competition.

BTW this also shows that having on-site employees is not a protection against frauds/thieves...